Hey there. I made a quick edit to show some things I think could be improved on this.

yours

edit (not animated)


So here is what I think:
The feet looks a little too much like balloons. Maybe it is the style you want, but I changed it in the edit. About your colors, I think that they were a little too dark, and there was too little contrast. I didn't change the contrast too much though, but you should experiment with it. Also, I changed most of the black outlines to colored outlines, because that often looks better. I think that his jacket had some gradient shading too so I changed that; try to not use gradient shading. I made his white shirt red but nevermind that. Some things that I didn't show in the edit: First of all, the coloring and shading of the pig. I recommend that you never use dithering in sprites, partly because I don't like it, and because it removes contrast ,(also it might be hard to animate, especially in more complex and bigger sprites). I think there should be another shade of grey on the wings. The grey used on the wings now I think should be used as the outline for the wings instead of black.

And short about animations:
These are cool animations, and congrats on making them so good because it would really be too bothersome for many people to do that. The walking animation I think could have smaller steps, right now they are almost like he's running. About the pig, I don't think it should fly so much up and down in the cycle, and perhaps you should try making the cycle faster, but it's nothing big.

Even if you don't make a game out of this, I think it is good practice to draw sprites and animate them. Well done. Remember to keep practiding, and with every picture you make you will become better